I bought my Neptune Apex a couple months ago and it came with the new temp and pH probes. The first month was great. Then the pH probe seemed to start reading low. Now about 2 months later you can't even calibrate it. It's not dirty. I tried calibrating it a few times here today and when I was done it was reading worse than when I started. I tested my pH with a hannah tester and the probe in the tank is reading 0.3 to 0.4 low. This is after calibration. Two months old.